Keep older chat history and image previews stable (#2490)

* fix(app): keep timeline history and previews stable

Treat persisted timeline replicas as display-only so authoritative pagination always comes from the daemon. Require renewed user intent between older-history pages unless the viewport genuinely remains at the history edge.

Model assistant image acquisition as loading, loaded, or failed so recreating a preview URL cannot be rendered as an error.

* fix(app): keep file image previews current

* fix(app): stabilize history pagination edges

* fix(app): recover transient timeline loads

* fix(app): retain assistant image previews

* Stabilize history pagination lifecycle

* Stabilize history settlement and image previews

* Retry file images after reconnect

* Keep active previews and pagination requests alive

* Replace image hook tests with typed ports

* Integrate timeline hydration with submission authority

* Harden pre-hydration timeline reconciliation

* Make rewind E2E use real scroll intent

* Preserve live timeline state through hydration

* Keep mounted image attachments retained

* Protect preview persistence and lifecycle hydration

* Preserve idless live assistant continuations

* Preserve timeline rows across delayed hydration

* test(app): cover real assistant image files

* Preserve assistant tool ordering during hydration

packages/app/src/hooks/use-load-older-agent-history.test.ts

@@ -84,7 +84,7 @@ describe("loadOlderAgentHistory", () => {
     const client = createClient();
     const inFlight = createInFlight();
 
-    await loadOlderAgentHistory(agentId, {
+    const started = await loadOlderAgentHistory(agentId, {
       client,
       cursor: undefined,
       hasOlder: true,
@@ -94,13 +94,14 @@ describe("loadOlderAgentHistory", () => {
 
     expect(client.calls).toEqual([]);
     expect(inFlight.values).toEqual([false]);
+    expect(started).toBe(false);
   });
 
   it("no-ops when the daemon says no older history exists", async () => {
     const client = createClient();
     const inFlight = createInFlight();
 
-    await loadOlderAgentHistory(agentId, {
+    const started = await loadOlderAgentHistory(agentId, {
       client,
       cursor: someCursor,
       hasOlder: false,
@@ -110,13 +111,14 @@ describe("loadOlderAgentHistory", () => {
 
     expect(client.calls).toEqual([]);
     expect(inFlight.values).toEqual([false]);
+    expect(started).toBe(false);
   });
 
   it("no-ops when a request is already in flight", async () => {
     const client = createClient();
     const inFlight = createInFlight(true);
 
-    await loadOlderAgentHistory(agentId, {
+    const started = await loadOlderAgentHistory(agentId, {
       client,
       cursor: someCursor,
       hasOlder: true,
@@ -126,13 +128,14 @@ describe("loadOlderAgentHistory", () => {
 
     expect(client.calls).toEqual([]);
     expect(inFlight.values).toEqual([true]);
+    expect(started).toBe(true);
   });
 
   it("requests the page before the current start cursor and clears in-flight on success", async () => {
     const client = createClient();
     const inFlight = createInFlight();
 
-    await loadOlderAgentHistory(agentId, {
+    const started = await loadOlderAgentHistory(agentId, {
       client,
       cursor: someCursor,
       hasOlder: true,
@@ -152,6 +155,7 @@ describe("loadOlderAgentHistory", () => {
       },
     ]);
     expect(inFlight.values).toEqual([false, true, false]);
+    expect(started).toBe(true);
   });
 
   it("shows a panel toast, warns, and clears in-flight on failure", async () => {